Lapping is a machining process by which two surfaces are abrasively rubbed together. Lapping generally takes one of two forms. The first form generally involves rubbing a work piece (e.g., a bar of hard disc drive heads) against a lapping plate with an abrasive (e.g., aluminum oxide, iron oxide, cerium oxide, other oxides, emery, silicon carbide, diamond) placed there between. This process forms microscopic conchoidal fractures as the abrasive rolls between the work piece and the lapping plate and removes material from both the work piece and the lapping plate. In some implementations, the abrasive is in a powder form and mixed with water or another liquid to form an abrasive slurry.
The second form of lapping generally involves rubbing the work piece against a lapping plate with an abrasive embedded in the lapping plate. For example, the lapping plate may be made up of a relatively soft material (e.g., pitch or a ductile metal) or a ceramic that holds the abrasive material and permits it to score the work piece when the work piece is rubbed against the lapping plate.
Lapping can be used to obtain a precise surface roughness and/or a very accurate surface contour (e.g., planar, convex, and concave). A lapping tool is used to provide precise dimensional control of the work piece to allow the lapping operations to achieve the desired surface roughness and/or contour on the work piece. The tool holds the work piece while it is lapped and permits precise control of the orientation of the work piece with respect to the lapping plate and fine adjustment of any load applied to the work piece during the lapping process.
Variations in surface roughness and/or contour may cause process difficulties or failures during later processing steps performed on the work piece. Further, variations in surface roughness and/or contour may cause poor performance of a resulting device. As a result, improved lapping equipment that makes tighter surface roughness and/or contour tolerances achievable and cost-effective is important to create smaller and more accurately defined devices (e.g., hard disc drive heads). Further, improved lapping equipment may achieve higher rates of material removal during the lapping process while maintaining the aforementioned surface roughness and/or contour tolerances.